Regulation by glucagon of serine: pyruvate/alanine: glyoxylate aminotransferase gene expression in cultured rat hepatocytes.
Regulation by glucagon of serine: pyruvate/alanine: glyoxylate aminotransferase gene expression in cultured rat hepatocytes.
复制标题
丝氨酸胰高血糖素的调节：丙酮酸/丙氨酸：培养的大鼠肝细胞中乙醛酸转氨酶基因的表达。
DOI：
10.1007/978-3-0348-7393-2_15
复制
发表时间：
1994
期刊：
影响因子：
--
通讯作者：
A. Ichiyama
中科院分区：
文献类型：
--
作者：
C. Uchida;T. Funai;T. Oda;K. Ohbayashi;A. Ichiyama
在原代培养的大鼠肝细胞中研究了胰高血糖素对丝氨酸：丙酮酸/丙氨酸：乙醛酸氨基转移酶（SPT/AGT）基因表达的影响。当肝细胞已预培养16-18小时的无血清和无血清的条件下，胰高血糖素的加入引起（约2小时的滞后期后）显着增加的SPT/AGT mRNA的细胞水平的4小时，在时间和剂量依赖性的方式。通过核糖核酸酶保护分析判断，诱导的mRNA为线粒体SPT/AGT。一个核运行的分析表明，转录的激活是负责线粒体SPT/AGT mRNA的增加，最大的转录速率发生在胰高血糖素添加后1.5小时。胰高血糖素的作用被8-溴-cAMP模拟，并被N-[2-（2-氨基乙基）-3-甲基-N-（2-氨基乙基）-3 cAMP依赖性蛋白激酶抑制剂[（对-溴肉桂氨基）乙基]-5-异喹啉磺酰胺（蛋白激酶A），而12-O-十四酰基佛波醇-13-乙酸酯和A23187都没有提高SPT/AGT mRNA水平的作用，提示cAMP/蛋白激酶A系统参与了SPT/AGT基因表达的调控。在无血清和无血清条件下预培养16-18 h的肝细胞中，胰高血糖素诱导的转录被放线菌酮严重抑制。另一方面，当预培养2小时时，胰高血糖素对转录的激活更快，放线菌酮的抑制作用低于预培养16-18小时的细胞，这表明一种短寿命的蛋白质因子参与了激素调节。胰高血糖素诱导的SPT/AGT基因表达也被地塞米松关闭。
The effects of glucagon on serine: pyruvate/alanine: glyoxylate aminotransferase (SPT/AGT) gene expression were studied in primary cultured rat hepatocytes. When hepatocytes had been precultured for 16-18 h under serum- and hormone-free conditions, the addition of glucagon caused (after a lag period of about 2 h) a remarkable increase in the cellular level of SPT/AGT mRNA by 4 h in a time- and dose-dependent manner. The induced mRNA was that for mitochondrial SPT/AGT, as judged by ribonuclease protection analysis. A nuclear run-on assay revealed that activation of transcription is responsible for the increase in mitochondrial SPT/AGT mRNA and that the maximal rate of transcription occurs 1.5 h after glucagon addition. The effect of glucagon was mimicked by 8-bromo-cAMP and suppressed by N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide, an inhibitor of cAMP-dependent protein kinase (protein kinase A), while both 12-O-tetradecanoylphorbol-13-acetate and A23187 were without effect in elevating the SPT/AGT mRNA level, suggesting that the cAMP/protein kinase A system is involved in the regulation of SPT/AGT gene expression. In hepatocytes precultured for 16-18 h under serum- and hormone-free conditions, the glucagon-induced transcription was severely inhibited by cycloheximide. When the preculture was for 2 h, on the other hand, the activation of transcription by glucagon was more rapid, and the inhibition by cycloheximide was less than that observed with cells precultured for 16-18 h, suggesting that a short-lived protein factor is involved in the hormonal regulation. The glucagon-induced expression of the SPT/AGT gene was also turned off by dexamethasone.